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Old 29th September 2011, 19:13   #1
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Default Surge Suppression required between car battery power supply and media player

Hi,

Want to know the power details and the features that happens during the car ignition. The amount of surge, voltage peak, current, voltage level details during ignition ON/OFF. what kind of supression can be used to remove this surge that happens during the ignition.
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Old 30th September 2011, 16:18   #2
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Default Re: Surge Suppression required between car batter power supply and media player

Hi,
May we know the intention of this study. Most of the ECUs shut down at voltages less than 6 - 7V.
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Old 30th September 2011, 18:38   #3
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Default Re: Surge Suppression required between car batter power supply and media player

The battery acts as a large current sink and suppresses most of the low frequency spikes. But at times, primarily due to frayed wiring, minor spikes occur. If the battery is on the brink, or if you are jump starting due to dead battery surge generated while starting can damage the ECU, hence many recommend switching the lights on in the car being started, giving the spikes an easier path.

Normally, the power to media switches off when the engine is switched on/off, most probably to prevent any voltage related damage. In case you want you can get a voltage cut off (usually based on the zenner diode) installed in the media power circuit, to limit high voltage spikes.

In older petrol vehicles a lot of RF noise was generated by the ignition circuit, and most of the cars after 70's came with an RF suppressor in the HT circuit.
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Old 30th September 2011, 21:00   #4
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Default Re: Surge Suppression required between car battery power supply and media player

Hi,
Contrary to popular belief (the battery is a super capacitor. Takes care of everything), the electrical environment in an automobile is extremely hostile for electronics. Most feared was the load dump!

However, what affects processors and ASICS is different from what affects linear circuits. So it would be useful if you could give details on why you want this data.

If for processors, there were a lot of white papers floating about in the mid eighties (when electronics started coming into autos in a big way). I guess you'll have to get hold of those. The ones I remember were all printed. Not soft copies.

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Old 1st October 2011, 02:53   #5
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Default Re: Surge Suppression required between car battery power supply and media player

Quote:
Originally Posted by anthiltg View Post
Hi,

Want to know the power details and the features that happens during the car ignition. The amount of surge, voltage peak, current, voltage level details during ignition ON/OFF. what kind of supression can be used to remove this surge that happens during the ignition.
The data you are asking for will vary from manufacturer to manufacturer, model to model and car to car. If all you want is a basic idea then the best is to get an oscilloscope from somewhere (all engineering college labs have it these days) and measure for yourself.


The suppression mechanism will depend upon what you want to suppress. If you want to suppress the surge to electronics - all the electronic systems should have power-management-units on their boards already with huge capacitors getting rid of momentary surges and shaping rise/fall time of supply voltage seen by chips.


Quote:
Originally Posted by Sutripta View Post
Hi,
Contrary to popular belief (the battery is a super capacitor. Takes care of everything), the electrical environment in an automobile is extremely hostile for electronics. Most feared was the load dump!

However, what affects processors and ASICS is different from what affects linear circuits. So it would be useful if you could give details on why you want this data.

If for processors, there were a lot of white papers floating about in the mid eighties (when electronics started coming into autos in a big way). I guess you'll have to get hold of those. The ones I remember were all printed. Not soft copies.

Regards
Sutripta


If he is buying pre-fabricated boards then he shouldn't have to worry about it - there will be capacitors and PMU on board that will ensure proper turn-on turn-off (no other modes allowed). If he is designing such a board then team-bhp is not the best place to fish for information, and frankly he should be more specific.


Battery-as-a-supercapacitor is a convenient fallacy but battery will not be very effective against very fast surges.




EDIT: Sorry, didn't see the post title earlier properly.

It is not clear whether by media player you mean audio player or video player. The latter will not be effected much due to any voltage fluctuations - or more precisely you will find it hard to tell.

However audio is a different matter - most amplifiers have relatively poor power supply isolation. You may want to invest in a small local power supply for the system (that may have its own battery).

BTW - I don't know about other cars, but in my Figo, whenever I turn ignition power to the audio is cut as far as I can tell.

Last edited by vina : 1st October 2011 at 03:22.
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Old 1st October 2011, 08:39   #6
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Default Re: Surge Suppression required between car battery power supply and media player

It would help if we knew what it was you are trying to solve.

1. Over-voltage of helper crank battery, when used

2. Under-voltage at ignition start

3. Isolation to reduce interference from other electronics causing poor quality audio stream.

All have slightly different solutions.
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Old 1st October 2011, 20:42   #7
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Default Re: Surge Suppression required between car battery power supply and media player

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Originally Posted by vina View Post
EDIT: Sorry, didn't see the post title earlier properly.

It is not clear whether by media player you mean audio player or video player.
A media player (I'm sure we are not talking of FM radio/ Cassette player combination) will have both a digital and an analog section. Both important. And affected differently.

Regards
Sutripta
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Old 1st October 2011, 22:23   #8
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Default Re: Surge Suppression required between car battery power supply and media player

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Originally Posted by Sutripta View Post
A media player (I'm sure we are not talking of FM radio/ Cassette player combination) will have both a digital and an analog section. Both important. And affected differently.

Regards
Sutripta

You are right sir - that is why I wrote that video may not be effected much, it is almot all digital (or less sensitive analog). Audio on the other hand has amplifiers, no matter how much digital is present, and they may not have the best power supply rejection.
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Old 2nd October 2011, 12:44   #9
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Default Re: Surge Suppression required between car battery power supply and media player

hi folks,

Actuall idea is to install pc(media/audio) inside the car. It would not be good to directly to put +12V battery directly interfaced to pc without having knowledge of understanding the behaviour of a battery, even though the system(carpc) has power supply management, This should not burden my pocket cost of direct mistake.
1. Is there any chances that power will go down below 6V due to car ignition. (in case yes why will that happen?)
2. what would be the spike range in volts or kilo volts? ( under voltage too?) How long will the spike remain?
3. Any simple circuit could be put in between battery and the carpc. (by mistake also the ECU should not get damaged)
4. Does it really going to have effect on audio quality if an isolation is provided between car pc and the battery.
5. Will there be any power fluctuation due to other electronics loaded in the car while running (ac, lights, power windows etc... ).


Best Regards
Thil
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Old 2nd October 2011, 13:35   #10
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Default Re: Surge Suppression required between car battery power supply and media player

Quote:
Originally Posted by cranky View Post
It would help if we knew what it was you are trying to solve.

1. Over-voltage of helper crank battery, when used

2. Under-voltage at ignition start

3. Isolation to reduce interference from other electronics causing poor quality audio stream.

All have slightly different solutions.

Was intersted in all specification that would give an idea what isolation could be used. would it be possible to have single solution for over voltage, under voltage and to keep up the audio quality good
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Old 2nd October 2011, 18:20   #11
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Default Re: Surge Suppression required between car battery power supply and media player

Quote:
Originally Posted by anthiltg View Post
Was intersted in all specification that would give an idea what isolation could be used. would it be possible to have single solution for over voltage, under voltage and to keep up the audio quality good
The only solution I can think of, that can take care of all your points, is to install an isolated power supply. This would be
. A DC-DC switching power supply taking input from the car battery and delivering conditioned power to your equipment.
. Similar supplies are used where the power may be "dirty", that is inconsistent voltage with a lot of noise and spikes.

Getting one may be a problem and costs are steep. Google to find more about this solution.
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Old 2nd October 2011, 20:14   #12
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Default Re: Surge Suppression required between car battery power supply and media player

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Originally Posted by Aroy View Post
The only solution I can think of, that can take care of all your points, is to install an isolated power supply. This would be
. A DC-DC switching power supply taking input from the car battery and delivering conditioned power to your equipment.
. Similar supplies are used where the power may be "dirty", that is inconsistent voltage with a lot of noise and spikes.

Getting one may be a problem and costs are steep. Google to find more about this solution.

Having ferrite bead or Resistor Capacitor does it make a difference!!. this should be low cost also. [Does it make sense.]
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Old 2nd October 2011, 20:38   #13
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Default Re: Surge Suppression required between car battery power supply and media player

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Originally Posted by anthiltg View Post
Having ferrite bead or Resistor Capacitor does it make a difference!!. this should be low cost also. [Does it make sense.]

What is the nominal supply voltage and peak current requirement of your application? Best is to buy a suitable supply unit rather than try designing your own.
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Old 2nd October 2011, 21:10   #14
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Default Re: Surge Suppression required between car battery power supply and media player

The best way for you to do this is to get a Pico PSU or other DC-DC-converter. These are readily available online.

In addition, you should add a timed delay for switch-on at the input of the PicoPSU to ensure it is not connected at the time of ignition. Normally the battery voltage may drop to about 10.5V or so at ignition. 6V means a dead battery that may not be able to turn the starter.

Another way to do this is power the PC off a dedicated battery and devise a circuit that decouples the two batteries till the car is detected to be putting out a steady state voltage.

All these can be designed with basic analog electronics or if you so wish, a microprocessor.

The DC-DC supply already has some level of protection built in. Most users report no issues with using them in default configuration with CarPC setups.

RC supplies will drop too much current, and LC will only help in some amount of ripple suppression. I would also not recommend using linear regulators to generate voltages for the motherboard, as might seem possible. They are going to waste a lot of power as heat. Even assuming a low-current 50W PC, you will be asking for the supply to handle at least 15W of heat, not very easy to dissipate inside the hot environment of a car.
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Old 3rd October 2011, 11:14   #15
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Default Re: Surge Suppression required between car battery power supply and media player

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Originally Posted by anthiltg View Post
Having ferrite bead or Resistor Capacitor does it make a difference!!. this should be low cost also. [Does it make sense.]
These are for RF suppression and not for voltage spikes and brown outs.

R-C is a waste of energy and used only where power requirement is very low. Instead for power electronics L-C rules. But this is a bulky and expensive solution compared to DC-DC route.
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